Exothermic reaction mixture and method of cast welding a copper base alloy utilizing same



Jan. 27, 1959 2,870,499

D. J. BURKE EXOTHERMIC REACTION MIXTURE AND METHOD OF CAST WELDING A COPPER BASE ALLOY UTILIZING SAME Filed Aug. 26, 1957 mmvma. DOA/0L0 J. BOX/(.

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United States Patent Donald J. Burke, East Cleveland, Ohio, asaignor to Erico Products, Inc., Cleveland, Ohio, a corporation of Ohio Application August 26, 1957, Serial No. 680,425

8 Claims. (Cl. 22205) This invention relates as indicated to a novel exothermic reaction mixture for producing a molten alloy, and more particularly for producing a molten alloy suitable for use in a method of welding whereby the ends of cables and the like may be joined together. Such reaction mixture is of the general type disclosed in Patent No. 2,229,045 to Charles A. Cadwell but is modified in certain substantial respects.

The welding material disclosed and claimed in such Cadwell patent has been very successfully employed in the cast welding of rail bonds to the sides of rails and for many other purposes. Such welding material comprises a mixture of copper oxide and a crushed copperaluminum alloy which when ignited will produce a charge of molten copper suitable for immediate use in the welding of a copper or copper alloy stranded conductor to a steel rail or the like. Patent No. 2,277,014 to Noble G. Carlson discloses a form of rail bonding apparatus particularly suited for use with the aforesaid welding material in the attachment of rail bonds to rails, such apparatus comprising two spaced mold blocks and common clamping means therefor adapted to clamp the same against the side of a rail head. Patent No. 2,654,129 to Edward B. Neif teaches an improved form of cast welding apparatus 1 adapted to be employed with the metal producing exothermic reaction mixture.

Because of the hightemperature evolved by the exothermic reaction, it is feasible, under properly controlled conditions, to perform a cast welding operation utilizing but a very small charge of the molten metal. This renders it practical and economical to perform such operations as 'the welding of small signal bonds to the heads of steel rails and to weld stranded conductors to pipe lines, for example. When handling such small bodies of molten metal, however,-there is obviously the problem of premature chilling before an adequate weld is obtained, and

this is particularly important when electrical connections are to be-made thereby. There must be a sufficient body of heat to achieve the weld. Small amounts of certain *fluxing agents may be of assistance but for certain types of work, such as the welding together of two opposed cable ends, it has in the past been necessary to utilize a somewhat larger amount of weld metal than would be desirable,

connection of somewhat greater diameter than the cable itself and also extending along or sleeving the respective cable end portions to some extent. While quite satisfactory for many purposes, this type of weld obviously forms an unsightly bump or lump when wrapped with insulating tape or the like and may not be acceptable where the cable is to be repeatedly wound and unwound on a drum as in the case of certain electrically driven mine cars, for example.

It is accordingly a principal object of my invention to 2 provide a method of producing cast welds having good electrical conductivity and high mechanical strength so that it may be employed in the formation of relatively small cast welds which will nevertheless have the requisite current-carrying capacity and mechanical strength to meet the conditions of use.

Still another object is to provide such cast weld connections which will not be brittle but will instead be mechanically strong and resistant to shock.

A further object is to provide an exothermic reaction mixture which is readily controllable, relatively inexpensive, and adapted to produce a molten alloy particularly effective for welding the ends of cables, bus bars and the like.

Other objects of my invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then consists of the means hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain approved compositions of matter and methods of employing the same, such disclosed composition and steps constituting, however, but certain of various ways in which the principle of the invention may be used.

In said annexed drawing:

Fig. l is a side elevational View of one preferred form I of cast Welding apparatus especially designed for the joining together of stranded cables;

Fig. 2 is a top plan view of such apparatus;

Fig. 3 is'a vertical section taken on the line 33 on Fig. 2;

Fig. 4 shows a cast weld connection as produced by my new apparatus and method; and

Fig. 5 illustrates such connection after trimming.

Referring now more particularly to such drawing and especially Figs. land 2 thereof, the embodiment of my invention there illustrated comprises two graphite crucible and mold blocks 1 and 2 mounted for movement toward and away from one another on guide pins 3 and 4, such blocks being hollowed out to form a vertically split crucible 5. The graphite blocks 1 and 2 are respectively engaged by and secured to (as by means of screws) supporting members 6 and 7 in the form of sheet metal stampings, these latter in turn being carried by frame members 8 and 9 pivotally joined at It]? for swinging movement whereby blocks 1 and 2 may be moved apart (pins 3 and 4 projecting but a short distance into block 2 and therefore capable of disengagement by such'swinging movement). Handle H is pivotally connected to frame member 8 at 12 and handle 13 is similarly pivotally connected to frame member 9 at 14, the inner ends of such handles themselves being pivotaliy joined at T5 to obtain a form of toggle acti0n,'p ivots 12, i4 and being in substantial alignment with one another when graphite blocks 1 and 2 are in closely juxtaposed position.

Crucible 5 will preferably be of downwardly tapering conformation, as illustrated, and provided with a central sprue passage 1'6 of somewhat smaller diameter than the bottom of the crucible. Such sprue passage then narrows'and descends vertically to a spherical cavity 17 defined by the opposed lower portions 13 and 19 of blocks 1 and 2 respectively. Such sprue passage is intersected by a transverse passage 2% likewise defined by the opposed graphite block portions 18 and i9 and being adapted to a receive the end portions 21 and 22 of stranded conductors or cables from which the insulation 23 and 24 has been stripped. The two semi-cylindrical grooves in the opposed faces of block portions 18 11214119 defining passage 20 will be dimensioned thus to receive the. stranded cable end portions and tightly to embrace and enclose the latter to prevent escape of molten weld metal dropping down from crucible 5 through sprue 16.

A graphite cover 25 will desirably be provided hinged by means of hinge 26 to block 2 and provided with a cavity 27 extending from the top of crucible 5 and opening laterally to permit the escape of gases produced by the exothermic reaction without danger of such gases, flame, and particles from the reaction mixture being blown upwardly toward the operators face.

After stripping the insulation from the cable end portions about 1 /2 inches from the end, such end portions 21 and 22 are inserted in passage with the two mold blocks slightly spaced apart. When the cable ends have been properly positioned, leaving a slight distance therebetween (usually about to Ms inch) as shown in Fig. 3 in vertical alignment with sprue passage 16, handles 11 and 13 will be moved apart to bring the two graphite blocks into close engagement with the cable ends clamped therebetween. The cables may additionally be clamped, if desired, beyond the mold to ensure against accidental displacement during the welding operation. A thin metal disk 28 which may be of steel, for example, and slightly dished, is next dropped into crucible 5 and positioned over the sprue opening as shown. When such disk has been seated, a cartridge of exothermic reaction material 29 of the general type disclosed in Cadwell Patent No. 2,229,045 may be inverted into the crucible with the ignition powder 30 on top. The cover 25 is now lowered into the position shown in Figs. 1, 2 and 3 of the drawing and a spark gun dis-charged into the opening 27 to ignite the starting powder 30. The exothermic reaction which immediately takes place produces the desired charge of molten copper metal which promptly melts through the disk 28 and drops down through sprue 16. The first molten metal which engages the ends of the stranded conductors 21 and 22 continues therepast into the lower cavity 17 and serves the purpose of preheating the end portions of the strands of cables 21 and 22 and also of heating the portions of the graphite blocks enclosing the latter. When cavity 17 has been filled by molten metal and likewise the lower portion of the sprue leading thereto, the following molten metal is intruded into the interstices between the preheated cable strands and flows a short distance in each direction along passage 20, merging with each individual strand and forming an integral weld therewith. The remaining portion of the molten metal charge accumulates in the upper portion of sprue passage 16 together with the lighter fluxing ingredients. After a delay of about ten seconds, handles 11 and 13 may be operated to move blocks 1 and 2 apart sufficiently to-permit Withdrawal of the cable ends and the cast weld joining the same. Such cast weld is shown in Fig. 4 including the spherical portion 31 formed in chamber 17 and the upper portion 32 formed in the upper portion of sprue 16. These two overflows, as they may be termed, may be trimmed away as shown in Fig. 5 to leave a cylindrical cast weld connection 33 of a diameter substantially that of the stranded cables 21 and 22. The exposed portions of such cables and the connection may now readily be covered with insulation which need not be of any greater thickness than the insulation 23 and 24, thereby achieving not only the best possible appearance but also avoiding a hump which would further limit flexibility of the cable at this point and is an impediment to proper winding and free travel of the cable.

In order that a cast weld connection of small size may have adequate physical strength and current-carrying capacity for difficult conditions of use, it is necessary that such small weld shall have improved grain structure and that it be thoroughly integrally joined with the individual conductor strands. To obtain such improved results, I modify the exothermic reaction mixture in the manner explained below.

I have found that if small amounts of certain nonferrous metals are incorporated in the exothermic reaction mixture in the proper manner to alloy with the molten copper produced thereby, the weld metal has an improved wetting effect on the metal parts with which it is intended to join, the molten weld metal may be produced at a somewhat lower temperature and therefore has less tendency to embrittle the strands of a cable or the like, and a very strong weld is obtained capable of withstanding rough handling in use. I have discovered, particularly, that a small amount of tin or silver incorporated in the reaction mixture or otherwise introduced to alloy with the molten weld metal produces an especially beneficial effect. The following specific examples of suitable exothermic reaction materials for producing weld metal in accordance with my invention are set forth for purposes of illustration only, and it will be understood that a variety of other formulations may be utilized instead, as explained below:

Example I Parts by weight Copper scale (roasted) 71.83 Copper-aluminum alloy, crushed (57% copper,

43% aluminum) 20.41 Calcium silicon 2.04 Fluorspar 2.04 Zinc oxide .68 Silver 3.00

v Example ll Copper scale (roasted); 73.69 Copper-aluminum alloy, crushed (50% copper,

50% aluminum) 18.48 Calcium silicon 2.07 Fluorspar 2.07 Zinc oxide .69 Silver 3.00

. 100.00 Example III Copper scale (roasted) 71.45 Copper-aluminum alloy, crushed (57% copper,

43% aluminum) 20.30 Calcium silicon 2.03 Fluorspar 2.03 Zinc oxide .68 Phosphorus-copper alloy copper, 15% phosphorus) 100.00 Example IV Copper scale (roasted) 73.30 Copper-aluminum alloy, crushed (50% copper,

50% aluminum) 18.38 Calcium silicon 2.06 Fluorspar 2.06 Zinc oxide .69 Phorphorus-copper alloy (85 copper, 15% phosphorus) 3.51

100.00 Example V Copper scale (roasted) 72.9 Copper-aluminum alloy, crushed (50% copper,

50% aluminum) 18.3 Calcium fluoride 2.1 Calcium silicon- 2,1 Zinc OJL 0,6 Tin metal 4 In producing the improved exothermic reaction mixtures of this invention. I utilize a reaction mixture such as that taught in Cadwell Patent 2,229,045, adding a small amount, ordinarily from about 2 to 8% of the alloying metal thereto, or preferably substituting such Parts by weight Copper scale (roasted) 74.05

Copper-aluminum alloy, (57 copper, 43

aluminum) 21.05 Calcium silicon 2.10 Fluorspar 2.10 Zinc oxide .70

When alloying metal such as tin or silver is added, the copper and aluminum will ordinarily each comprise about 50% of the copper-aluminum alloy (see Example V above, which is a pre ferre d embodiment of this invention).

The small amounts of calcium silicon, fluorspar and zinc oxide included in the several foregoing mixtures afford a desirable fluxing action and enhance the soundness of the weld metal. When a thin steel disc is utilized to close the sprue opening of the crucible, the metal therefrom will likewise be incorporated in the weld metal when it is melted by the heat of the exothermic reaction but inasmuch as such disc is ordinarily extremely thin, the amount of iron added thereby is usually inconsequential.

The copper producing exothermic reaction mixture last listed above may be modified by substituting for a portion of the copper present as metal a generally equivalent amount of silver, phosphorus, zinc, tin, or aluminum in amounts ranging from about 2 to about 8% of the total weight of the reaction mixture. Thus, the amount of copper in the copper-aluminum alloy may be reduced somewhat so that the heat of the molten metal produced by the exothermic reaction mixture would be rather greater than desired if it were not for the presence of the alloying metal intermixed therewith. With the exception of phosphorus and zinc, the indicated alloying metals may be dispersed through the reaction mixture in granular or finely divided form, but it is generally preferred that they be incorporated in that part-of the mixture lying in the lower part of the crucible and this is quite important in the case of materials such as phosphorus and zinc having relatively low boiling points. This may be done in the case of silver, for example, by silver-plating the sprue closure disc or even forming such disc of a very thin sheet of silver. The zinc, tin and aluminum may be similarly employed. The phosphorus may desirably be incorporated in the form of a phosphorus-copper alloy as indicated above. Such alloy is very brittle and may simply be provided in the form of small lumps in the bottom of the crucible or bonded together with water glass (sodium silicate), for example, to form the sprue closure disc. In general, any nonferrous alloying ingredient which it is desired to employ in the copper producing exothermic reaction mixture and which has a relatively low boiling point (i. e. below about 3500 F.) should be placed at or near the bottom of the crucible inasmuch as the exothermic reaction between the aluminum and the copper oxide, even though modified by the presence of copper as metal in the amounts indicated, is sufficient to generate a momentary localized temperature on the order of 4000 F. Silver which has a boiling point of 3634 F. may be dispersed throughout the reaction mixture with satisfactory results 6 although it may be preferred to concentrate the silver in the lower part of the crucible where the heat is not as intense. With alloying elements boiling below about 3000 F. it becomes very desirable to place the same in the lower part of the crucible and with those boiling below 2500 F. it is most important.

Utilizing a copper producing exothermic reaction mixture conforming to the formulation last given above, but with 4% granular tin metal incorporated in the mixture, a cast weld was produced which was physically strong and not brittle under impact. The weld metal was employed to splice together two /2 inch diameter copperbus bars, and it was found that a weld of no greater diameter than the bars had excellent currentcarrying capacity and excellent strength under all conditions of use.

I prefer to employ an amount of tin metal in the reaction mixture to yield only from about /2% to about 10%. by weight of tin in the resultant copper-tin alloy which is adapted to be employed in the welding operation. More especially, I prefer to employ from about 3% to about 5% tin metal by weight in the exothermic mixture. The tin metal employed in the exothermic reaction mixture may be either granular tin (20 to 40 mesh) or pulverized tin. A typical suitable example of the latter included 73% passing through 325 mesh, 15% on 325 mesh, 2% on 200 mesh, 6% on 180 mesh, and 5% or less on mesh.

Utilizing the principles of my invention I am enabled to produce sound welds of copper metal alloyed with small amounts of other elements to improve the physical characteristics of the weld despite the fact that the amount of weld metal produced may be so small as to have but a small reservoir of heat to effect the weld.

With small welds, such as those joining copper cable ends and bus bars, it is important to preheat the surfaces to be welded. Otherwise, such surfaces will so cool the weld metal due to their high conductivity that only a partial weld will be obtained, if indeed any. The alloying materials specifically mentioned enhance the wetting ability of the molten copper and also improve the strength of the finished weld. Good electrical conductivity may moreover be maintained.

I have found that my new welding composition incorporating therein tin metal in a relatively small amount is particularly satisfactory for the purposes indicated and is furthermore relatively inexpensive.

This application is a continuation-in-part of my co-' pending application Serial No. 422,032, filed April 9, 1954, which in turn is a division of my prior application Serial No. 331,634, filed January 16, 1953, now Patent No. 2,801,914.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. An exothermic reaction mixture for producing a molten copper alloy comprising approximately Parts by weight 2. In an exothermic reaction mixture for producing a molten copper alloy comprising a mixture of copper oxide and a sufficient amount of aluminum to reduce said oxide, and sufiicient copper as metal efiective to absorb a substantial amount of the heat generated by the reaction,

all being finely divided; tin metal admixed therewith in an amount effective to constitute from V2% to 10% by weight of the molten metal resulting from such exothermic reaction.

3. An exothermic reaction mixture according to claim 2, wherein such tin metal constitutes from about 3% to about 5% by weight of said mixture.

4. An exothermic reaction mixture for producing a molten copper alloy suitable for use in forming strong non-porous electrically conductive welds, comprising a major amount of copper oxide, a reducing agent effective to reduce said amount of oxide, an amount of copper metal intimately associated therewith effective to absorb a substantial part of the heat of the reaction and to be melted to form a portion of the molten product, and from about 2 to about 8 parts of tin metal by weight admixed therewith.

5. The exothermic reaction mixture of claim 1, including a small amount of a fluoride flux.

6. The exothermic reaction mixture of claim 1, including a small amount of a flux, and wherein said reducing agent is aluminum.

7. The exothermic reaction mixture of claim 1, wherein said tin metal is included in an amount effective to constitute from /2% to 10% by weight of the molten metal resulting from such exothermic reaction.

8. The method of cast welding together the'opposed ends of two stranded copper conductor cables which comprises producing a small charge of molten copper by an exothermic reaction, alloying from about /2% to about 10% tin therewith, by weight of the total alloy, dropping a portion of such molten alloy against such opposed cable ends to pre-heat the same with such portion continuing downwardly past such ends to solidify in a region substantially spaced therefrom, dropping a further portion of such molten alloy closely following such first portion against such pre-heated cable ends confined in a mold closely embracing the same, whereby such further portion of such alloy will flow a short distance along the respective cable end portions and wet and weld the same, allowing such alloy to solidify, and then trimming away the solidified first portion of such alloy and any excess solidified above the cable end portions to leave a cast weld connection of substantially the same diameter as such cable end portions.

References Cited in the file of this patent UNlTED STATES PATENTS 2,229,045 Cadwell Ian. 21, 1941 2,238,926 Cadwell Apr. 22, 1941 2,282,175 Emerson May 5, 1942 2,337,314 Deppeler Dec. 21, 1943 

8. THE METHOD OF CAST WELDING TOGETHER THE OPPOSED ENDS OF TWO STRANDED COPPER CONDUCTOR CABLES WHICH COMPRISES PRODUCING A SMALL CHARGE OF MOLTEN COPPER BY AN EXOTHERMIC REACTION, ALLOYING FROM ABOUT 1/2% TO ABOUT 10% TIN THEREWITH, BY WEIGHT OF THE TOTAL ALLOY, DROPPING A PORTION OF SUCH MOLTEN ALLOY AGAINST SUCH OPPOSED CABLE ENDS TO PRE-HEAT THE SAME WITH SUCH PORTION CONTINUING DOWNWARDLY PAST SUCH ENDS TO SOLIDIFY IN A REGION SUBSTANTIALLY SPACED THEREFROM, DROPPING A FURTHER PORTION OF SUCH MOLTEN ALLOY CLOSELY FOLLOWING SUCH FIRST PORTION AGAINST SUCH PRE-HEATED CABLE ENDS CONFINED IN A MOLD CLOSELY EMBRACING THE SAME, WHEREBY SUCH FURTHER PORTION OF SUCH ALLOY WILL FLOW A SHORT DISTANCE ALONG THE 